TDA7272A Datasheet, PDF (10/16 Pages) STMicroelectronics – HIGH PERFORMANCE MOTOR SPEED REGULATOR

TDA7272A
Figure 14.
Figure 15.
Inverting input of main amplifier. In this pin the
current reference programmed at pins 20, 17 is
compared with the current from the monostable
(stream of rectangular pulses).
In steady-state condition (constant motor speed)
the values are equal and the capacitor C_F voltage
is constant.
This means for the speed n (min 1):
n
=
10.435
C_T k R_P
where ”k” is the number of collector segments.
(poles)
The non inverting input of the main amplifier is in-
ternally connected to a reference voltage (2.3 V).
Figure 16.
Pin 15
Ground.
Pin 16
Ground.
Pin 17
Left speed adjustment. The voltage at this pin is
fixed to a reference value of 0.8 V. A resistor from
this pin and ground (fig. 14) fixes the reference
current which will be compared with the medium
output current of the monostable in order to fix the
speed of the motor at the programmed value. The
correct value of Rp would be :
R_P
=
10.435
C_T k n
n = motor speed, (min -1)
k = poles number
The control of speed can be done in different
way:
- speed separately programmed in two
senses of rotation (fig. 14-15) ;
- only one speed for the two senses of rota-
tion (fig. 16) ;
10/16
Figure 17.
- speeds of the two senses a bit different (i.e.
for compensating different pulley effects)
(fig. 17) ;
- speed programmed with a DC voltage (fig.
18) i.e. with DA converter ;